The notion that there was a list of arrests already prepared is sure to fuel speculation that President Erdogan himself staged the coup.

The swift rounding up of judges and others after a failed coup in Turkey indicated the government had prepared a list beforehand, the E.U. commissioner dealing with Turkey's membership bid, Johannes Hahn, said Monday.

"It looks at least as if something has been prepared. The lists are available, which indicates it was prepared and to be used at a certain stage," Hahn said.

"I'm very concerned. It is exactly what we feared,” he added.

Following a failed coup attempt on Saturday, Turkish authorities have already rounded up 6,000 people in the armed forces and judiciary for allegedly backing the coup.

Erdogan said that a purge of this "virus" would continue.

The notion that there was a list of arrests already prepared is sure to fuel speculation that President Recep Tayyip Erdogan himself staged the coup as a pretext to further consolidate his power.U.S.-based cleric Fethullah Gulen has accused the president of staging the coup.

Meanwhile, Erdogan accuses Gulen of being the mastermind behind the coup and has called for him to be extradited to Turkey.

He said a "terror group" led by Gulen had "ruined" the armed forces, that its members were being arrested in all military ranks. Gulen denied any connection with the coup.

Reports indicated that in the weeks before Friday's coup attempt, Erdogan had been planning to purge high-ranking officers who supported Gulen.

According to the pro-government Turkish newspaper the Daily Sabah, one of the items on the agenda at the meeting was a pending decision on “more than 1,000 military personnel who have alleged connections to the Gulen Movement and are charged with military espionage.”

Before the insurrection had even been completely put down, Erdogan called it a “gift from God,” and claimed it provided him with a reason to “cleanse” the military.

The Foreign Ministry raised the death toll stemming from the coup attempt to more than 290, including over 100 rebels, and said 1,400 people were hurt.